The Psyches: the Cases 



Let us go a step farther in our explora- 

 tions. For the soft, yielding wadding col- 

 lected from a plant, or the down gleaned 

 from the wing of a Moth, we will substitute 

 rough stone. In their final state, I know, the 

 Psyches' cases are often laden with grains of 

 sand and earthy particles; but these are acci- 

 dental bricks, which have been inadvertently 

 touched by the spinneret and incorporated 

 unintentionally in the thatch. The delicate 

 creatures know too well the drawbacks of a 

 pebbly pillow to seek the support of stone. 

 Mineral matter is distasteful to them; and it 

 is mineral matter that now has to be worked 

 like wool. 



True, I select such stones in my collection 

 as are least out of keeping with the feeble 

 powers of my grubs. I possess a specimen 

 of flaky hematite. At the rmerest touch of a 

 hair-pencil it breaks into atoms almost as 

 minute as the dust which a Butterfly's wing 

 leaves on our fingers. On a bed of this ma- 

 terial, which glitters like a steel filing, I esta- 

 blish four young caterpillars extracted from 

 their clothing. I foresee a check in this ex- 

 periment and consequently increase the num- 

 ber of my subjects. 



227 



